1. Field of the Invention
The present invention relates to rolling and more particularly to a mill stand roll assembly.
The mill stand roll assembly of the present invention can be used in section and wire rolling mills.
The invention is readily applicable in other industries where an accurate adjustment of the mutual axial disposition of two shafts may be required, as, for example, in disk shears for setting up disk blades or in straightening machines.
2. Description of the Prior Art
There is widely known a mill stand roll assembly comprising two grooved rolls arranged in parallel with one another and intended for passing therebetween billets in order to effect the rolling thereof.
Each of the rolls has end necks coaxial with the roll, each free end of said necks having a thrust shoulder.
Each thrust shoulder is placed inside a thrust double-sided hydrostatic bearing set in a chock serving as a housing for said bearing and secured to the roll housing.
The hydrostatic bearing has thrust disks each arranged on both end faces of each shoulder substantially parallel thereto. The sides of the disk facing the end faces of the thrust shoulder have hydrostatic pockets communicating with a fluid source through an orifice in body of the disk. As is readily apparent to those skilled in the art that the hydrostatic pockets are recesses in the body of the disk near the orifice for supplying the liquid. Said recesses are intended to receive the liquid under pressure and create a hydrostatic pressure field in the gap between the disk and the shoulder balancing the axial load applied to the shoulder.
In the construction under consideration, there is a single fluid source of constant delivery communicating with all the hydrostatic pockets through throttling valves.
In the known roll assembly, the mutual arrangement of grooved rolls, i.e. the accuracy of alignment of roll grooves, is determined by the mutual position of the shoulders with respect to the housing, this being ensured by an adequate setting of the thrust bearings with respect to the housing.
However, in the process of rolling the rolls tend to move one with respect to the other within the clearances and the deformations of the thrust bearings. This displacement is governed by the axial force applied to the rolls and by the rigidity of the hydrostatic bearings, said rigidity being substantially a function of the hydraulic resistance of the throttling valves.
The displacement of the rolls causes a change in the mutual positions of the roll grooves, this resulting in poor accuracy of the manufactured items.
Parallel with this, the displacement of the rolls causes a redistribution of the gaps between the thrust shoulder and the disks, more specifically: the gap between the shoulder and the loaded disk decreases, whereas that between the shoulder and the non-loaded disk increases. Accordingly, the disk taking up the load is subject to more severe service conditions than the non-loaded one. The adjustment of the mutual arrangement of the grooved rolls in the known roll assembly necessitates the stoppage of the mill, this lowering the efficiency thereof.